Level density of 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mo>+</mml:mo></mml:msup></mml:math>states in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>40</mml:mn></mml:msup></mml:math>Ca from high-energy-resolution (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><

Usman, I. T.; Buthelezi, Z.; Carter, J.; Cooper, G.R.J.; Fearick, R. W.; Förtsch, S. V.; Fujita, H.; Kalmykov, Y.; Neumann-Cosel, P. von; Neveling, R.; Poltoratska, I.; Richter, A.; Shevchenko, A.; Sideras‐Haddad, E.; Smit, F. D.; Wambach, J.

doi:10.1103/physrevc.84.054322

Cited by 22 publications

(71 citation statements)

References 51 publications

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“…The (E o À E a ) ¼ 22 meV obtained in this work agrees with the activation energy of Bi-induced acceptor levels reported by Pettinari et al, which is 26.8 AE 0.5 meV [32]. Besides, the value of 22 meV is slightly larger compared to the calculated binding energies of 8 to 17 meV (for Bi triplets) for Bi-induced energy levels that act as localized centers for carriers [12].…”

Section: Results and Discussion 31 Evidence Of Localization Effectssupporting

confidence: 91%

“…Our previous study found that the band gap of GaAs 1Àx Bi x reduces linearly at a rate of 64 meV/%Bi for x up to 0.06 [35]. However, this work shows that for higher Bi concentrations, the band gap reduction becomes nonlinear, as already reported in the literature by several groups [11][12][13]34]. Figure 4b shows the HR-XRD spectra of a GaAs 1Àx Bi x sample with x ¼ 0.108 (thickness of 30 nm).…”

Section: Band Gap Of Gaasbisupporting

confidence: 76%

“…Hence, the PL peak energy at low temperatures does not represent the energy of the band gap. The localized states may be attributed to Bi inhomogeneity and clustering as a result of the limited solubility of Bi in GaAs and the low growth temperature [12,14]. The large FWHM at 10 K (>63 meV compared to 13 meV for GaAs) also indicates significant Bi inhomogeneity in the sample.…”

Section: Results and Discussion 31 Evidence Of Localization Effectsmentioning

confidence: 99%

“…It was proposed that the incorporation of Bi into GaAs increases the valence band maxima as a result of an anti-crossing interaction between the valence band of GaAs and Bi resonant states [11]. Recently, Usman et al reported that, in addition to the anti-crossing interaction, the energy of the conduction band also reduces linearly with Bi concentration by 28 meV/%Bi as expected under the virtual crystal approximation [12]. A downward movement of the conduction band has also been demonstrated experimentally by Batool et al [13].…”

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confidence: 88%

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Localization effects and band gap of GaAsBi alloys

Mohmad

Bastiman

Hunter

et al. 2014

Phys. Status Solidi B

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The structural and optical properties of GaAs1−xBix alloys for x up to 0.108 have been investigated by high resolution X‐ray diffraction and photoluminescence (PL). At room temperature (RT), the PL intensity of the GaAs0.97Bi0.03 sample was found to be ∼300 times higher than a GaAs control sample grown at the same temperature (400 °C). PL measurements carried out at 10 K show that when excitation power, Pex was increased from 0.11 to 1140 W cm−2, the PL peak energy blue‐shifts by 80 meV while the full‐width‐at‐half‐maximum reduces from 115 to 63 meV. However, the PL peak emission energy becomes independent of the excitation power at RT. The results indicate the presence of localized energy states in the GaAs0.97Bi0.03 sample, which trap carriers at low temperatures and that the majority of the carriers become delocalized at RT. Furthermore, the temperature dependent PL also shows an S‐shape behavior, which is a signature of localization effects. A theoretical model, which was derived by solving a rate equation was employed. The model successfully reproduces the observed S‐shape behavior and the theory fits well with the experimental data. The RT band gap of GaAs1−xBix for x up to 0.108 has been plotted and compared with the literature.

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Section: Results and Discussion 31 Evidence Of Localization Effectssupporting

confidence: 91%

Section: Band Gap Of Gaasbisupporting

confidence: 76%

Section: Results and Discussion 31 Evidence Of Localization Effectsmentioning

confidence: 99%

mentioning

confidence: 88%

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Localization effects and band gap of GaAsBi alloys

Mohmad

Bastiman

Hunter

et al. 2014

Phys. Status Solidi B

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“…It has been found that the most stable results are obtained by setting σ 0.5 · ∆E and σ > /σ = 2.5 − 3.5 in agreement with the results of Refs. [39,49]. The spectra g(E x ) and g > (E x ) for the present data are shown in Fig.…”

Section: A Fluctuation Analysismentioning

confidence: 88%

Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

et al. 2014

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Background: The electric isovector giant dipole resonance (IVGDR) in208 Pb has been measured with high energy resolution with the (p, p ) reaction under extreme forward angles [A. Tamii et al., Phys. Rev. Lett. 107, 062502 (2011)] and shows considerable fine structure.Purpose: The aim of the present work is to extract scales characterizing the observed fine structure and to relate them to dominant decay mechanisms of giant resonances. Furthermore, the level density of J π = 1 − states is determined in the energy region of the IVGDR.Methods: Characteristic scales are extracted from the spectra with a wavelet analysis based on continuous wavelet transforms.Comparison with corresponding analyses of B(E1) strength distributions from microscopic model calculations in the framework of the quasiparticle phonon model and the relativistic random phase approximation allow to identify giant resonance decay mechanisms responsible for the fine structure. The level density of 1 − states is related to local fluctuations of the cross sections in the energy region of the IVGDR, where contributions from states with other spin-parities can be neglected. The magnitude of the fluctuations is determined by the autocorrelation function.Results: Scales in the fine structure of the IVGDR in 208 Pb are found at 80, 130, 220, 430, 640, 960 keV, and at 1.75 MeV. The values of the most prominent scales can be reasonably well reproduced by the microscopic calculations although they generally yield a smaller number of scales.. The inclusion of complex configurations in the calculations changes the E1 strength distributions but the impact on the wavelet power spectra and characteristic scales is limited. The level density of 1 − states is extracted in the excitation energy range 9 − 12.5 MeV and compared to a variety of phenomenological and microscopic models. Conclusions:In both models the major scales are already present at the one-particle one-hole level indicating Landau damping as a dominant mechanism responsible for the fine structure of the IVGDR in contrast to the isoscalar giant quadrupole resonance, where fine structure arises from the coupling to low-lying surface vibrations. The back-shifted Fermi gas model parameterization of Rauscher et al., Phys. Rev. C 56, 1613 describes the level-density data well, while other phenomeological and microscopic approaches fail to reproduce absolute values or the energy dependence or both.

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Gamma Strength Functions and the Brink-Axel Hypothesis

Neumann-Cosel

2020

Compound-Nuclear Reactions

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Level density of 2+states in40Ca from high-energy-resolution (p,<

Cited by 22 publications

References 51 publications

Localization effects and band gap of GaAsBi alloys

Localization effects and band gap of GaAsBi alloys

Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

Gamma Strength Functions and the Brink-Axel Hypothesis

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